Phenoloxidase activity and virulence in isogenic strains of Cryptococcus neoformans.
A naturally occurring Mel- variant of Cryptococcus neoformans was isolated from the wild type. The effect of phenoloxidase activity on virulence was analyzed on genetically constructed Mel+ and Mel- isolates. The traits Mel+ and virulence in mice, as measured by cumulative mortality and replication potential in brain tissue, cosegregated among the progeny of a Mel+ X Mel- cross. Revertants (MelR) isolated during the course of the cumulative mortality experiment were used to compare virulence in isogenic sets of Mel- and MelR. In two separate sets of such isolates, Mel+ phenotype and virulence coreverted. Measurement of substrate uptake and phenoloxidase activity showed that loss of detectable phenoloxidase was the basis for the Mel- phenotype and that enzyme activity reappeared in the MelR isolates. An intermediate phenotype, Melbg, was also described. Cosegregation and coreversion of the melanin phenotype and virulence suggest that phenoloxidase is a virulence factor in C. neoformans.
D004156:Catechol Oxidase / Q000378:metabolism*; D003454:Cryptococcus / Q000472:pathogenicity*; D003455:Cryptococcus neoformans / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity*; D008543:Melanins / Q000096:biosynthesis; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D009154:Mutation
D008543:Melanins; D004156:Catechol Oxidase; D014442:Monophenol Monooxygenase